Frequency-changer.



PATENTED JULY 9, 1907; E. P. W. ALEXANDERSONQ FREQUENCY CHANGER. APPLICATION TILED AUG.- 24. 1906.

2 sums-4112M 1.

fr/7st E VL AL rands/"$00 ccy No. 859,359. PATENTED JULY 9, 1907. E. F. W. ALEXANDERSON.

FREQUENCY CHANGER. APPLIOATIOI FILED AUG. 2-1, 1905.

2 SHEETS-SHEET 2.

5/7756 5 Aexandersm q ue nc y.

UNITED STATES P "IFEET OFFTGE.

QUENCY Qpecificatiin:

Filer-tars NEW YORK, ASSIGNOR TO GENERAL .JN (ll? NEW YORK.

Application filed August 2%. 19%. 8erinl H0. 27,571.

To all whom it may concern:

Be it known that I, Enns'r F. W. ALEXANDERSON, a subject of the King of Sweden, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Frequency-(hangers; of which the following is a specification.

My invention relates to dynamo-electric machines adapted to transform an alternating current of one frequency into a current of a different frequency, and its object is to produce a simple and efficient form of machine for this purpose.

It is well understood in the art that induction motors, driven mechanically from an external source of power, and having one winding supplied with alternating current, will serve to transform the current with respect to its frequency, the relative frequency of the currents in the primary and secondary windiugs depending upon the speed-at which the machine is driven. frequency of the current induced in the secondary winding will he the same as that supplied to the primary winding. If the secondary winding is driven in the same direction as the revolving field produced by the primary winding the secondary frequency Thus, if both windings are stationary the 1 will be less than the primary, becoming zero when the a machine of the induction-motor type that it coniblues in itself both the transforming windings for producing a change in frequency and also the driving means for imparting to the transforming windings the rice ary speed of rotation. I accomplish. this by providing the machine with two sets of windings with different numbers of poles, one set acting as motor windings to drive therotating member with reference to the stationary member and the other set acting as tiansftu-im-r windings to receive current of one fretpicucy and to deliver current of another fre- Since the two windings are of two different numbers of poles each setof windings acts indepenrt ently of the other though both are mounted on the same magnetic core.

My invention further consists in arranging, for the purpose above set forth, a machine having the structure of a standard induction motor with both members wound in the usual way with uniform distributed coils. I accomplish the desired result by connecting the coils on each member so that they form elee: {neatly two separate windings of different pole numbers. Further, in order to obtain I the minimum reactance of both motor and transformer windings I arrange the connections so that each winding is distributed through all "the slots, or in other words, so that each slot contains conductors of both windings.

My invention further consists in providing means for compounding the frequency change: for variations in load, and in this feature of my invention it is not iimited to a frequency chauger' having both motor and transformer windings on the same cores. M y invention in this aspect consists in providing means responsive to variations of current in the motor windings for controlling the voltage of the transformer windings. More specifica ly stated I employ a series tr isforiner having its primary in series with one of the motor windings and its secondary in series with one of the transformer windings.

My i vention further comprises the use of a series transformer of a special type which will lie liclcinafter described.

My invention will best be understood by reference to the accompanying drawings, in which Figure; slim diagrammatic-ail};a-frequency changer arranged in accordance with my invention with both stator and rotor windings developed on a plane sur face; Fig. 2 shows 'a simplified diagmm of connections; and Fig. 3 shows the preferred arrangement of the compounding transformer.

In Fig. l A represents the stator core which in practice woifld consist of a slotted laminated body similar in every respect to the stator of a standard induction motor, Y represents the rotor core which in practice would consist of a slotted luuinated drum like the rotor of a standard induction motor. Both the stator and rotor cores are wound in the manner usual in a standard induction motor, with uniform distrilmted coils. The i coils on each member are connected. electrically to form two independent windings. Thus, on the stator core A there are formed two separate three-phase windings: tliephases of one winding are indicated by l, 2 and 3, respectively, and. are shown in heavy, light and dotted lines respectively, while the phases of th other winding are indicated by 4", 5 and (3. in order to avoid coin'usion, the end connections of the two windings shown on opposite sides of the core. lly tracing out any one phase the lirstnientioned winding, for-instance thephase 3, it will be seen that this winding is six-pole winding, while by tracing out use 4 it will he that the other winding is a loin-pole The two windings on the core A are connected in parallel, through compounding, transformer windings which will be herein explained, to a source of three-phase -current indicated by the line wires 1, 2 and 3. The windings on the core A are consequently the primaries of the motor and transformer windings of the machine. It will be understood, however, that while I have shown the two primary windings on the stator core either or both may be placed on the rotor core if preferred, the'only essential being that the primary and secondary windings of each set, whether transformer or motor, should be placed on opposite cores. The two windings on the rotor core B are shown arranged similarly in every respect to the primary windings on the core A. Thus, the three phases 1, 2 and 3 of one winding correspond in pole number to the six-pole stator winding, while the second rotor winding having the phases 4, 5" and 6" form a four pole winding. As in the case of the stator. the two windings are shown with their end connections made on opposite sides of the core.

It will be seen that the same number of slots are indicated on both stator and rotor. The reason for this is that for the sake of simplicity the slots on both cores are shown of the smallest possible number. In practice, however, the number of slot's on each member a would be much larger and in that case the two cores should be given different numbers of slots conforming to the standard induction motor numbers, in order to avoid the locking tendency which exists where both cores have the same number of slots.

It will be seen that the four-pole rotor winding is short-circuited upon itself, so that coacting with the four-pole'winding it will drive the rotor core at a speed corresponding to that of afour-pole induction motor. The six-pole rotor winding on the other hand is connected to collector rings from which a secondary circuit of different frequency may be supplied. That the four-pole windings act as the motor windings to the machine and the sixpole windings act as the transformer windings. Since the windings are of different numbers of poles, each set will act entirely independently of the other, although both sets are carried on the same cores.

The operation of the machine is then as follows: If

three'phase current with a freqneneyior instance of 25 cycles is supplied to the primary six-pole winding, while the primary four-pole winding is open-circuited so that the machine is stationary, an electromotive force will be induced at the collector rings C having a frequency of 25-cycles. Now if the primary motor winding is supplied with current at 25 cycles and if the primary motor winding is connected to produce a rotating field opposite in direction to that of the transformer winding the rotor will be driven in a' direction opposite to that of the rotation of a transformer --field,- at a speed corresponding to that of a four-pole motor running on a. 25 cycle current. The secondary transformer winding is now consequently driven at a speed, relative to the rotating transformer field, equal to the sum of the actual speed of rotation of the rotor and the rotation of the transformer field. The frequency induced at the collector ring is consequently increased in the ratio of 4 to (4+6),.that is, 4 to :10. With a constant strength of transformer field the voltage is also increased in the same proportion. Thus,

for instance. if, with the rotor standing still, the secondary transformer winding produces a voltage of 90 at a frequency of 25, then. when the motor windings are energized the secondary transformer winding will produce a voltage of approximately 220 at a frequency orgy, so that the machine has an advantage in this re spect over a simple motor-generator set such as is sometimes used for a frequency changer.

In order to maintain a constant voltage at the collector rings C with varying load, or if desired, to produce a rising voltage with increase of load I provide an arrangement of transformer windings as shown. In series with each phase of one of the motor windings is inserted a primary transformer winding, while the secondary of the transformer is connected in series with a phase of one of the transformer windings of the machine. The secondary windings of the compounding transformer windings are indicated at I, 2 and 3, the numerals corresponding to the phases 1". 2 and 3 of the transformer winding of the machine in series with which they are connected. The primary compounding transformer windings are indicated as 4,- 5 and 6 corresponding to the phases of the motor windings in series in which they are connected. An increase of load in the circuit supplied from the collector rings C, produces a proportional increase of current in both the motor and transformer windings of the machine, and by means of the series transformer I am able to utilize the increased current in, the motor windings to maintain or to increase the voltage delivered by the machine to the secondary circuit.

For compounding in the manner just described, I prefer to employ a special compounding transformer of the type described inmy former patent No. 805.253, granted to me Nov. 2], 1905. This compounding transformer is essentially a transformer 'so arranged that: the compounding voltage is approximately in phase with the line voltage ,irnpressed 0n the circuit to be compounded, and at the same time the roactance drop in-the secondary winding of the compounding transformer, due to current flow in'the compounded circuit is substantially in quadrature with the line voltage so that the voltage in the compounded circuit is practically unaffected thereby even with great variations of current flow in the compounded circuit. Such a result may be readily obtained by constructing a transformer with an open magnetic circuit and connecting the primary and secondary windings of the transformer in different phases of the circuit to be compounded and of the circuit the current flow orwhich is utilized for compounding. This connection of primary and secondary in different phases is shown in Figs. 1 and 2 and the construction of the transformer is shown somewhat diagrammatically in Fig. 3. In Fig. 3 a

I frequency-changer arranged in accordance with my.

three-phase transformer T is shown so arrangcd that each leg of the magnetic circuit contains an air gap. The two windings on each leg are connected in different'phases of the motor and transformer winding respectively of the machine, as is clearly shown in Fig. 2. Thus, the primary winding l of the compounding transformer is connected in series with the phases 4" of the motor winding which is connected to line wire I while the corresponding secondary winding 3 of the compounding transformer is connected in series with the phate 3 of the transformer winding of the machine which -is connected to line wire 2. In this arrangement, because of theopcn magnetic circuit oftion of the windings the compounding elcctromotive force which is added to the line voltage by secondaries of the compounding transformer is substantially in phase with the line voltage notwithstanding the dephasing effect on the relative phases of primary and secondary electro-motive forces produced by forming the transformer with an open magnetic (tin cuit, this dephasing effect being compensated for by connecting the primary and secondary windings in different; phases; that is, the added eleetromoti e' force is in proper phase for most; efficient compounding.

It will be understood that my invention is not liinited to the particular number of poles or phases, or the specific arrangem ent'and connections of the several windings shown in the drawings, but that all these featuresmay be modified as desired to meet varying requireiitents. Furthermore the machine may: he used to transform from a lower to a. higher frequency .as well as from a higher to alower. Thus the particular machine-shown in the drawings might be used equally well to transform from 25 to cyices.

It will *he understood that I have shown the windings of the machine diagrammatically and that in practice any suitable type of winding may be employed. A form of winding particularly adapted for use in a invention is shown and described in my former application, Serial Xo. 274,856, filedAugust 19, 1905.

nectcd to an alternating current circuit. and one of the two other windings being short-circuitcd and the other councctvd to a second alternating current circuit of different frequency.

2. In a frequency changer. a stationary member. a to tatable member. two primary windings of dificrent pole numbers both electrically connected to a source of alter hating current. and two secondary windings of correspondshortcircuited and the other provided 'itb terminals adapted for connection to an external circuit, the primary and secondary windings of each number of poles being carricd the one by the stationary member and the other by the rotatable member.

:2. In a frequency changer. a stationary member. a to. tatablemember. a pair of transformer windings carried by said members respectively and connected to two circuits of different frequency. and a pair of motor windings of differ our pole number from the transformer windings carried by said mciubon: respectively. the primary motor winding heiug connected to the same circuit with the primary transformer winding. I

4. In a frequency changer, a stationary member, a rotzttrble member. a pair of polyphase transformer windings carried by said members reispoctively and connected to two polyphase circuits of different frequency. and a pair of polyphaso motor windings of different pole number from the transformer windings carried by said members respectively. the primary motor winding being connected to the same circuit with the primary transformer winding in such manner as to produce relative rotation of the,trans-- former windings in the opposite directinnto the rotation of the transformer field relative to the secondary transformer winding. r

5. In a frequency changer. a stationary magnetic core wound with uniform distributed coils connected to form two separate windin 's of different pole numbers. and a rotatable core similarly wound. the pole numbers of the rotatable windings corresponding to the stationary windings respectively. one winding of each pole number being connected to an alternating-current circuit. and one of the remaining windings being shorL-eircuitcd and the other connected to a second alternatingcurrent circiiit of (littercnt frequency.

G. in a frequency changer. a stationary ma netic core wor d with uniform distributed coils connected to form two separate windings of different pole numbers. and a rotatable core similarly wound. the pole numbers of the rotatable windings corresponding to the stationary winiings respectively. the two windings of one pole number being connected as motor windings to drive the rotatable core, and the two other windings being connfitcd as transformer windings in primary and secondary alternating current circuits; of diiferent treqnency.

7. In a frequency changer. a primary magnetic core wound with uniform distributed coils connected to form two separate windings of different: pole numbers. both of said windings being connected to a primary alternating current circuit. and a secondary core similarly wound. the two secondary windings corresponding in pole numbers to the primary windings respectively. one of said secondary windings being short-circuited and the other connected to a secondary alternating-current circuit of ditt'erent Ire,- qucncy from the primary circuit.

S. In a frequency changer, a primary magnetic core wound with uniform distributed coils connected to form two separate polyphasc windings of different pole numbers. said two windings being connected to a primary altermtting-currcnt circuit iif such manner as to product r0 tilting fields in opposite. directions in said core. and :1 sec ondary core similarly wound. the secondary winding-s corresponding in pole numbers to the primary windings. one of said secondaries being shortcircuitcd and the other conneeted to a secondary circuit of higher frequency than the primary circuit.

9. In a frequency changer. two rclativelyinorable magnetic cores. and two windings of different pole numbers on each core. both windings on one core being connected to the same alternating-cnrrent circuit. and one of the wind iugs on the other core being connected to :1 second alterhating-current circuit and the other short-eircuited.

10. In a frequency changer, two relatively movable magnetic cores. each wound with uniform distributed coils electrically connected to form two separate windings of different pole numbers. both windings on one core being connected to the same alternatingenrrent circuit. and one of the windings on the other core being connected to a secon'd alternating'current circuit and the other short-ciring polo numbers, one of said secondary windings being 1 cnited.

11. In a frequency changer, a stationary slotted magnetic core wound with uniform distributed coils connected to form two separate windings of different pole numbers. each slot containing conductors of both windings. and a rotatable slotted core similarly wound. one winding of each pole number-being connected to an alternating-con rem circuit. and one of the two remaining windings being short-circuited and the other connected to a second circuit of diilert-nt frequency.

1;. In a frequency changer. a stationary magnetic core. two windlngsof different pole members carried tlo-reby. a rotatable magnetic core. and two windings carried thereby corresponding in pole numbers to the stationary'windings. the two windings of one pole number being connected as motor windings to drive the rotatable core. and the other two windings being connected as transformer windings in primary and secondary altcruatlug-current circuits of. different frequency.

12:. In a fre uency changer. a stationary slotted masuctic ('0l't"\\'ullllti with uniform distributed ooils connected to form two separate windings of diiiert-nt poltnlilllbers. each slot containing ct'inductors of both windings. and a rotatable slotted core similarly wound. the two windings of one pole number being connected as motor windings to drirc th rotatable core, and the other two windings being connected as transformer windings in prinmry and secondary alternattug-current circuits of dilferent frequency.

14. In a frequency changer. two pairs of windings. ontwinding of each pair being stationary and the other rotatable and the two rotatable windings being mechanically connected. one pair of windings being connected as mot r windings to drive the rotatable winding and the other pair being connected as trztnsi'urnh-r windings in primary and secondary tlternating-current cil'cilitshi' diTtert-nt frequency. and means responsive to variation in current in the tnotor windings for increasing the voltage delivered to said secondary circuit.

13. In a frequency changer. two pairs of \\in(]ii\f'\' one winding 01' each pair being stationaryand the other rotatable and the two rotatable windings being mechanically connected. one pair of windings being count-cred as motor windings to drive the rotatable windin' s and the otherpair being connected as transformer tidings in primary and secondary alternating-current circuits of ditferent frequency and a series transformer having its windings conported in series with a motor winding and with a transformer winding respectively.

11;. in a frequency changer. two pairs of windings. one winding of each pair being stationary and the other rotatable and the two rotatable windings being mechanically connected. one pair of windings being connected as motor wvindings to drive the rotatable windings and the other pair being connected as transformer windings in primary and secondary alternating-current circuits of difierent frcqucncy. and voltage controlling means adapted to compensate for increase in load. 17. In a frequency changer. a istationar' magnetic core. two windings of di' 'erent [)uik numbers carried thereby. a rotatable magnetic core, two windings carried thereby corresponding in pole numbers to the stationary windin the two windings of one pole number being connected as motor windings to drive the rotatable core. the other two windings being-connectet'i as transformer windings in primary and secondary alternating-curretit circuits of different frequency, and voltage controlling means adapted to compensate for increase in load.

18. In a frequency changer. a stationary magnetic core.

two windings of different pole numbers carried thereby. a rotatable magnetic core. two windings carried thereby corresponding in pole numbers to the stationary windings. the two windings of one pole number being connected as motor windings to drive the rotatable core. the other two windings being connected as transformer windings In primary and secondary alternating-tairrcnt circuits of differcnt frequency. and means responsive to variation in current in the motor windings for increasing the voltage of the transformerwindings.

in. in a frequency changer. a stationary magnetic core. two windings of different pole numbers carried therebr. a rotatable magnetic core. two windings carried ther by corresponding in pole numbers to the stationary windings. the two windings of on pole number being connected as motor windings to drive the rotutable core. the othcl two windings being connected as'transformer windings in primary and secondary alternating-current circuits of different frequency. and a series transformer having its windings connected in series with one of said motor wind.- ings and with one of said transformer windings respectively.

H. In a frequency changer. a'stationary magnetic c re. two poiyphase windings of different pole numbers carried thereby. a rotatable magnetic core. twopolyphase wind ings carried thereby corresponding in pole numbers to the stationary windings. the two windings of one pole number being connected as motor windings to drive the rotatable core. the other two windings being connected as transformer windings in'priinary and secondary alternatin current. circuits of diftferent frequency. and a transformer of the open core type having .a secondary winding in scrics with a phase of one of said transformer windings and a primary winding in inductive relation to said secondary winding and connected in series with a dilferent phase of one oi said motor windings.

21. In a frequency changer. two pairs of polyphasc windings. one winding of each pair bring stationa v and the other rotatable and the two rotatable windings being int-chimit-ally connected. one pair of windings being connected as tnotor windings to drive the rotatable windings and tip other pair being connected as transformer-wind ings in primary and secondary alternatingcurrent circuits of dilferent frequency. and a transformer of the open core type having a secondary in series with a phase of ou ot said tr: nst'ormt-r windings and a primary winding in inductive relation to said secondary winding and connected in series with a different phase of one of said motor windings.

2'. in a dynamo-electric machine. two relatively movable sl tted magnetic cores each wound with distributed coils all ot' the same width forming mechanically a single winding but electrically conn cted to form two separate winding 's of diilerent pole numbers. v

23. in a dynamo-electric machine, two relativel movable slotted magnetic cores each wound with distributed coils all of the same width forming mechanically a single winding but electrically connected to form two seprate windings of different pole numbers cacl'i slot on each cortcontaining conductors of both windings.

-ln \\'iillt.-=.s whereof I have hereunto set my hand this 23rd day ot August. lhofi.

ERNST F. W. ALEXANDERSUN. Witnesses I iirxunix B. IIt'LL, 'rliznns flurouo. 

